Post by thread:Exposure times to erase EPROM PICs?

I'm having trouble erasing 16C64 EPROM parts with my UV eraser lamp -- they take way too long to erase (three or four times as long as 27xxx EPROMs take). Is this normal? What kind of times should I expect? Frank ------------------------------------------------------------------------ Frank A. Vorstenbosch +31-(70)-355 5241 spam_OUTfalstaffTakeThisOuTxs4all.nl

In a message dated 95-10-02 17:43:35 EDT, you write: >I'm having trouble erasing 16C64 EPROM parts with my UV eraser lamp -- >they take way too long to erase (three or four times as long as >27xxx EPROMs take). > >Is this normal? What kind of time You will probably find that only the configuration bits (especially the code protect bits) are what is taking so long. uChip has increased the robustness of the code protect bits to reduce the possibility of the CP bits erasing first thus allowing someone to read out the code from a protected part.

> >I'm having trouble erasing 16C64 EPROM parts with my UV eraser lamp -- > >they take way too long to erase (three or four times as long as > >27xxx EPROMs take). > > You will probably find that only the configuration bits (especially the code > protect bits) are what is taking so long. uChip has increased the robustness > of the code protect bits to reduce the possibility of the CP bits erasing > first thus allowing someone to read out the code from a protected part. Yes, that sounds right: the last fuse to go in my experiment of three 16C64s was the CP fuse -- it took more than twice as long as the code itself. The code took about twice as long to erase as a 27128. Examining the chip I wonder where the config fuses are. The EPROM array is clearly visible, and next to it is a small structure that *could be* the configuration fuses. Is this really so, or has uChip buried the config fuses in the code EPROM array? ------------------------------------------------------------------------ Frank A. Vorstenbosch +31-(70)-355 5241 .....falstaffKILLspam@spam@xs4all.nl

>Examining the chip I wonder where the config fuses are. The EPROM >array is clearly visible, and next to it is a small structure that >*could be* the configuration fuses. Is this really so, or has uChip >buried the config fuses in the code EPROM array? I am clueless on this subject. But I'd bet that if you can see it without a microscope it ain't an EPROM cell CP fuse or not.

Jim Scorse <JScorseKILLspamAOL.COM> wrote: > > Examining the chip I wonder where the config fuses are. The EPROM > > array is clearly visible, and next to it is a small structure that > > *could be* the configuration fuses. Is this really so, or has > > uChip buried the config fuses in the code EPROM array? > >I am clueless on this subject. But I'd bet that if you can see it >without a microscope it ain't an EPROM cell CP fuse or not. Fortunately, Jim, Microchip has been kind enough to publish a poster-sized photograph of the die. You can probably get one of these "Revolutionary 8-Bit Microcontrollers" 16C64 posters from your local Microchip rep. -Andy -- Andrew Warren - .....fastfwdKILLspam.....ix.netcom.com Fast Forward Engineering, Vista, California

>Fortunately, Jim, Microchip has been kind enough to publish a >poster-sized photograph of the die. You can probably get one of these >"Revolutionary 8-Bit Microcontrollers" 16C64 posters from your local >Microchip rep. >-Andy Gee... my very own pinup. Look at the feature size on that one!

> I'm having trouble erasing 16C64 EPROM parts with my UV eraser lamp -- > they take way too long to erase (three or four times as long as > 27xxx EPROMs take). > > Is this normal? What kind of times should I expect? > > Frank Frank, My experimentation revealed 5 minutes USUAL time and 7 to 8 for a good, reliable erase. I am using the least expensive eraser I could fine too. I is designed to erase up to 6 chips at one time and my time is for one. -- -- Paul Greenwood -- (EraseMEpablospam_OUTTakeThisOuTaustin.ibm.com) Ask not for whom the telephone bell tolls ... if thou art in the bathtub, it tolls for thee.